1. Field of the Invention
The present invention relates to an improvement in air conditioner, particularly of a type that the capacity of its compressor is controlled responding with change of the load of cooling or heating.
2. Prior Art
FIG. 14 is a block diagram of an example of a conventional air conditioner of the type where capacity of the compressor is controlled responding with change of air condition load. The air conditioner comprises a refrigerant circuit connecting a compressor f, an indoor heat exchanger a, an expansion valve e and an evaporator g connected through tubes in that order to form a closed circuit of the refrigerant. In the conventional air conditioner, a pair of thermisters b and c are mounted on the input end part and the output end part of the indoor heat exchanger to measure the temperatures at the respective end parts, and the thermisters b and c are connected to the input terminals of a control circuit d, output terminal of which is connected to the expansion valve e to control it so as to change flow rate of the refrigerant thereby.
In such conventional air conditioner, when the flow resistance against the refrigerant flow of the indoor heat exchanger a is large, the temperature difference across the thermister b and c becomes large. Then, it is not easy to correctly detect the condition of the refrigerant at the output end part c, and hence, it is not easy to accurately control the condition of the refrigerant flowing into the compressor f. Furthermore, the conventional thermal-electric type valve has generally a slow response speed and hence hardly be used in air conditioners. Moreover, the conventional thermal-electric type valve can handle fluid in only one direction. Therefore, even if a thermal-electric type valve could be made to have a high response speed, it would still be necessary to use a pair of such valves connected parallely in opposite directions in case of all-season type air conditioner, where refrigerant flows in one direction for cooling the room and in the opposite direction thereto for heating the room.